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Biomedical subjects

U Banerjee

Publications and source records attributed to U Banerjee.

At least 73 records · Page 4Linked to original sources
PubMed1990

Defective plasma membrane H(+)-ATPase or orthovanadate resistant mutants from Candida albicans, a pathogenic yeast.

Orthovanadate-resistant mutants of diploid yeast Candida albicans were isolated by using two step mutational process. Such mutants had altered plasma membrane H(+)-ATPase activity. Based on the levels of PM-ATPase activity, these mutants could be grouped into two categories; one group included those mutants which did not exhibit reduction in PM-ATPase activity while the other displayed a reduction of upto 40% in enzyme activity. These mutants exhibited a number of distinct phenotypic characteristics and altered abilities with regard to phenotypic divergence. Results demonstrate the importance of PM-ATPase in overall physiology of this pathogenic yeast.

Animals↗
PubMed1989

Cladosporiosis (cerebral phaeohyphomycosis) of brain--a case report.

A case of cerebral cladosporiosis caused by Cladosporium trichoides (bantianum) now known as Xylohypha bantiana is described and illustrated. Predisposing debilitating diseases were not detectable. The Cladosporiosis diagnosis was based on visualisation of hyphal element in direct Gram's stain, direct KOH preparate of pus from brain abscess and on repeated successful cultivation of Cladosporium trichoides from specimen and by histopathology. Following surgery and anti-fungal chemotherapy the patient was cured.

Adult↗
PubMed1989

Cockroaches as vectors of pathogenic bacteria.

One hundred and thirty two cockroaches of species Blattella germanica--96 from hospital ward (test group) and 36 from residential areas (control group) were caught during Nov. 1985 to Nov. 1986. A variety of pathogenic and non-pathogenic bacteria were isolated from test and control group of insects. Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus faecalis, and Micrococci were isolated only from the test group of cockroaches. A high percentage (98.95 per cent) of test cockroaches were found to be carriers of various microorganisms as compared to the control group (80.55 per cent), the difference being statistically significant (p less than 0.001). Quantitative analysis in this study revealed that higher number of microorganisms are carried by test group of insects in the hospital environment. This, thereby suggests that these insects can play an important role in the etiology of hospital acquired infections.

Animals↗
PubMed1988

NMR study of the interactions of polymyxin B, gramicidin S, and valinomycin with dimyristoyllecithin bilayers.

The interactions of three polypeptide antibiotics (polymyxin B, gramicidin S, and valinomycin) with artificial lecithin membranes were studied by nuclear magnetic resonance (NMR). Combination of 31P and 2H NMR allowed observation of perturbations of the bilayer membrane structure induced by each of the antibiotics in the regions of the polar headgroups and acyl side chains of the phospholipids. The comparative study of the effects of these membrane-active antibiotics and the lipid bilayer structure demonstrated distinct types of antibiotic-membrane interactions in each case. Thus, the results showed the absence of interaction of polymyxin B with the dimyristoyllecithin membranes. In contrast, gramicidin S exhibited strong interaction with the lipid above the gel to liquid-crystalline phase transition temperature: disordering of the acyl side chains was evident. Increasing the concentration of gramicidin S led to disintegration of the bilayer membrane structure. At a molar ratio of 1:16 of gramicidin S to lecithin, the results are consistent with coexistence of gel and liquid-crystalline phases of the phospholipids near the phase transition temperature. Valinomycin decreased the phase transition temperature of the lipids and increased the order parameters of the lipid side chains. Such behavior is consistent with penetration of the valinomycin molecule into the interior of the lipid bilayers.

Dimyristoylphosphatidylcholine↗
PubMed1987

The sevenless+ protein is expressed apically in cell membranes of developing Drosophila retina; it is not restricted to cell R7.

In the sevenless (sev) mutants of Drosophila, a single cell type, photoreceptor R7, does not develop. We made monoclonal antibody against a sev+-beta-galactosidase fusion protein, and used it to determine the ultrastructural localization of the sev+ protein in the larval eye disc. The protein is expressed on the apical surface of the developing retina. It is not restricted to cell R7; it is expressed in all the presumptive photoreceptor cells, cone cells, and possibly others. The protein localizes to the cell membranes of the apical tips and their microvilli, away from the bulk of the cell-cell contacts. Possible mechanisms for generating the specificity of the sev phenotype are discussed in light of these results.

Animals↗
PubMed1987

Molecular characterization and expression of sevenless, a gene involved in neuronal pattern formation in the Drosophila eye.

The Drosophila sevenless mutation results in lack of a single neuron (photoreceptor cell R7) in every ommatidium of the compound eye; the developmental defect occurs in the larval eye disc. We created P-element-induced alleles and used them to isolate the sev gene. An 8.2 kb transcript is expressed in the eye disc, behind the morphogenetic furrow, coincident with recruitment and differentiation of photoreceptor clusters. The transcript becomes localized at the apical surface, persists in the prepupa, and fades out at pupation. It is again detected in the adult head. In some alleles the 8.2 kb transcript is absent. In others, the transcript is expressed, in spite of the absence of cell R7. Localization of the gene product in the eye disc was obtained with antibody raised against sev protein.

Alleles↗
PubMed1985

Interaction of alamethicin with lecithin bilayers: a 31P and 2H NMR study.

The interaction of alamethicin with artificial lecithin multilamellar dispersions was investigated by nuclear magnetic resonance (NMR) and Raman spectroscopies. 31P NMR studies revealed perturbation of the lipid head groups in the presence of the icosapeptide. Simulation of the 31P NMR spectra indicated that the observed spectral changes could be attributed to slight variations in the average tilt angle of the head groups. In contrast, no noticeable effect of the peptide on the segmental order of the hydrophobic acyl chains of the lipid molecules was detected by 2H NMR and Raman spectroscopic measurements. Taken together, these results indicated that, in the absence of a transmembrane electric potential, alamethicin interacts primarily at the water-lipid interface without significant insertion or incorporation into the bilayer leaflet.

Alamethicin↗
PubMed1984

NMR spectroscopic identification of a hexacyanochromate(III) binding site on Pseudomonas azurin.

Studies of redox reactions between the blue copper protein azurin and inorganic reagents have suggested the formation of discrete complexes between the reaction partners prior to the actual electron-transfer step. To get an insight into the structural nature of the complexes formed, we have studied the interaction (i) between oxidized Pseudomonas aeruginosa azurin and the anion Fe(CN)6(3-) and (ii) between reduced azurin and Cr(CN)6(3-). At low ionic strengths, stoichiometric binding of one Fe(CN)6(3-) ion to the oxidized protein is observed. In the high-resolution proton magnetic resonance spectra of the reduced protein, specific broadening of the assigned residues is observed upon titration with the redox-inert Cr(CN)6(3-) ion. Analysis of this paramagnetic spectral broadening in terms of the three-dimensional structure of the protein has led to the proposal that the binding site of the anions lies approximately midway between lysine residues 85 and 92. Evidence in support of this conclusion is provided by parallel studies on Alcaligenes faecalis azurin, which lacks these lysine residues. A similar site on the surface of Pseudomonas azurin has recently been identified by affinity labeling with chromous ions as an electron-transfer locus [ Farver , O., & Pecht , I. (1981) Isr . J. Chem. 21, 13-17]. The results presented here suggest that this region on the protein surface also may be employed by anionic electron-transfer agents.

Alcaligenes↗
PubMed1983

Structure of alamethicin in solution: nuclear magnetic resonance relaxation studies.

An NMR relaxation study at 500 MHz of the icosapeptide antibiotic alamethicin is reported. This study lends further support to the partly helical, partly extended, amphiphilic, and dimeric structure recently proposed for this peptide in methanolic solutions [Banerjee, U., Tsui, F. P., Balasubramanian, T. N., Marshall, G. R., & Chan, S. I. (1983) J. Mol. Biol. 165, 757]. The N-acetyl methyl groups toward the N terminus of alamethicin in this solvent system were found to exhibit unusual NMR relaxation behavior. The decay of the transverse magnetization due to these protons was nonexponential, but the spin-lattice relaxation recovery of the longitudinal magnetization was exponential. In a solution saturated with urea, however, both decays were exponential. These observations are shown to be consistent with the proposed structure. Studies in water yielded qualitatively similar but more complex results. The transverse relaxation times suggest further aggregation in water and indicate that the larger aggregates in water may be made up of the smaller units observed in methanol.

Alamethicin↗
PubMed1983

Structure of Alamethicin in solution. One- and two-dimensional 1H nuclear magnetic resonance studies at 500 MHz.

We report here the 500 MHz 1H nuclear magnetic resonance spectra of Alamethicin, an icosapeptide antibiotic isolated from Trichoderma viride, in methanol, water and methanol/water mixtures. At this frequency, resonances from all the protons are well-resolved in methanol and may be assigned unambiguously. Spectral assignments were made using two-dimensional spin-echo correlated spectroscopy and by spin-decoupling experiments. The amide coupling constants (JNH-alpha CH) facilitated conformational predictions, which were confirmed in part by two-dimensional nuclear Overhauser experiments. On the basis of these data, we propose a secondary structure for Alamethicin that is alpha-helical toward the N terminus and extended beta-sheet at the C-terminal end. This structure is consistent with earlier circular dichroism measurements (McMullen et al., 1971), infrared attenuated total reflection spectroscopy studies (Fringeli & Fringeli, 1979) and proton exchange data (Davis & Gisin, 1981). The proposed structure is a tightly bound dimer, wherein the beta-sheet is stabilized by intermolecular hydrogen-bonds between opposing molecules. An interesting feature of this structure is that it exhibits both a hydrophobic and a hydrophilic surface. This highly amphiphilic nature of the dimer structure may account for the extensive further aggregation of Alamethicin in water. The 1H n.m.r. spectrum of Alamethicin in water is broad, suggesting extensive association. However, spectral assignments and amide coupling constant measurements in water, which were accomplished by titration of methanolic solution of Alamethicin by water, revealed no gross changes in the basic secondary structure of the molecule.

Alamethicin↗
PubMed1982

The phospholipid packing arrangement in small bilayer vesicles as revealed by proton magnetic resonance studies at 500 MHz.

Proton magnetic resonance spectra of saturated phospholipids in small unilamellar vesicles has been recorded at 500 MHz on a Bruker WM500 spectrometer. The additional spectral dispersion reveals new structure in the acyl chain resonances. At temperatures near the thermal phase transition, the chain methylene and methyl peaks are split, both showing a broad and a relatively sharp component. Magnetization transfer experiments together with studies in the presence of manganese ions inside or outside the vesicles indicate that the sharp component is to be assigned to the protons from the acyl chains in the inner half of the bilayer and the broad component to chains in the outer monolayer. These experiments demonstrate unambiguously that the extreme surface curvature intrinsic to small unilamellar vesicles induces a profound asymmetry in the packing arrangement of the hydrocarbon chains in the two leaflets of the bilayer and causes the two monolayers to exist in markedly different motional states.

Aged↗
PubMed1982

Antistress and antifatigue properties of Panax ginseng: comparison with piracetam.

The antistress and antifatigue properties of a Chinese ginseng preparation were tested on Swiss albino mice, exposed to various experimental models of stress, and were compared with those of piracetam. Both ginseng and piracetam were administered chronically in drinking water for 16-18 days as well as acutely, by injection, 30-60 min prior to the experiments. Reactivity of the mice, loss in body weight, amount of faeces, length of endurance and incidence of mortality were graded and measured. Both piracetam and ginseng treatment provided good protection against electroshock stress when compared to the untreated mice; fighting scores, incidence of tonic convulsion and mortality were significantly less in the treated groups. In the heat stress experiments, both piracetam and ginseng provided significant protection to the treated mice against exposure to heat. In the fatigue stress of forced swim test, ginseng treatment provided effective adaptation to fatigue and increased endurance in both male and female mice; piracetam showed some antifatigue effects on the male mice only. In the locomotor activity tests, ginseng did not depress motility, while piracetam did so in the later part of the tests. These results are discussed in the light of the antistress properties of the drugs as reported in the literature.

Adaptation, Psychological↗